Detonation meter



FEM

7,, ESQ

Filed Feb. 29, 1944 D. R. DE BOISBLANC DETONATION METER 1o 12 I3 9 1013 14 11 13 1s 20 23 11 K L:- r

22 1 25 PlCK QWGHC f MPuHE PULSE ACCUMULATOR VACUUM UP PASS ANo TUBE P1 1.1- E R THRESHOLD VOLT METER e 7 a 15 1s 19 17 21 32 30 1 27 RECTANGULAR coUNTER o PULSE 0 AND 0 GENERATOR DISCHARGER 33 24 as i ,29 3| 3s 42 46 25 1=1c1 HIGH AMPLIFIER SQUARE c SQUARE L Accum- 0: UP PASS AND PULSE PULSE U1.AT0R *2 i FILTER THRESHOLD GENERATOR GENERATOR Q 33 AND CONSTANT vAR1AB1.E 2 7 a PULSER HEIGHT HEIGHT 47 -5 l5 lo 3 34 37 43 44 50 48\ 39 ACCUMULATOR 4 33 B1AS1N AND 0 OVOLTAGCE o I DISCHARG\ER GENERATOR 41 4O 2 Elm 49 AINVENTOR .R. BOISBLANC FIG-2 D Feb. 7, 1950 m. R. DE BOISBLANC DETONATION METER 3 Sheets-Sheet 2 Filed Feb. 29, 1944 INVENTOR D.R. dc, BOISBLANC AORNES We. 7, 1950 D. R. DE BOISBLANC DETONATION METER 3 Sheets-Sheet 5 Filed Feb. 29

INVENTOR D.R. do BOISBLANC UNITED STATES PATENT OFFICE DETONATION METER Deslonde R. de Boisblanc, Bartlesville, Okla assignor to Phillips Petroleum Company, a corporation of Delaware Application February 29, 1944, Serial No. 524,502

16 Claims.

i This invention relates to methods of and means for indicating the intensity of detonation of an internal combustion engine, and it has particular relation to determining the intensity level of detoand method which will give the average value, or sum, of n detonations where n is any predetermined integer.

Another object is to provide a detonation meter nation, or knocking, by electronic means designed and method in which the uniformity of knocks to be in substantial agreement with the results above a threshold value may be observed and the obtained by the human ear, but to determine the total value of n of such knocks read by a comparintensity level with a higher degree of accuracy atively unskilled operator, the indicating hand and with less skilled operators than possible with being substantially at rest at the time of making the car. the readings.

In the prior art of testing fuels for octane number in a test engine, the knocking was listened for by ear in conjunction with observations on a cathode ray tube of the rate of change of pressure Another object is to provide in a detonation meter and method of measuring detonations a means and method of counting and adding pulses of variable value in groups of n pulses where n in the cylinder. The ping which is heard when is any predetermined integer.

the engine is knocking is the sound generated by A further object is to accomplish the above pressure waves in the cylinder setting up vibralisted objects without introducing any new factions of between 5,000 and 17,000 cycles per sectors into the prior art of rating of the fuel by ear ond. It is old to pick up the pressure changes in and do so with a minimum of parts, minimum the cylinder with a magneto-striction type indicost and ease of operation.

cator manufactured by the Standard Oil Com- Other objects are to provide methods and appany of California which generates a voltage subparatus useful in signalling and indicating and stantially proportional to the rate of change of still further objects and advantages will be appressure and to observe the 12,000 to 17,000 cycle parent to those skilled in the art upon reading variations in voltage indicative of detonation by the following specification, claims and drawings. impressing the generated voltage on the leads. of In the drawings:

a cathode ray oscillograph. The intensity of Figure 1 is a diagrammatic view of a detonaknocking was still judged by ear however, as it tion meter embodying my invention with the cirproved impossible to measure the rapid fine wave cuit elements arbitrarily separated as to function form produced. Attempts to measure the wave and with the probable electrical wave form transform electronically have not proved acceptable to mitted from one circuit element to the next shown the industry because the octane ratings obtained adjacent the respective elements.

were not in agreement with the octane ratings of Figure 2 is a similar view of a modified form the same fuel made by ear and/or were not reof detonation meter embodying my invention. producible. While the ear is not as sensitive as Figure 3 is a circuit diagram of a portion of an electronic device to small changes in knock the apparatus shown in Figure l.

intensity, it is very accurate as to the approximate Figure 4 is a circuit diagram of a portion of the knock intensity if the operator is skilled. Beapparatus shown in Figure 2.

cause of past ratings of fuel by ear and because Figure 5 is a circuit diagram of one preferred the ultimate consumer of fuel judges by car it is form of the many suitable types of regulated therefore desirable to follow ear rating standards.

The principal object of this invention is to devise a method of and apparatus for indicating the intensity of detonation in a cylinder of an internal combustion engine which indication will be in substantial agreement with that obtained by the human ear of a skilled operator, but which indication will be more accurate than observations made by the ear and which will not require the high skill of an operator trained to rate detonation intensities by ear.

Another object is to provide an electronic device and method which will give the degree of knock intensity in an easily readable manner.

by the Standard Oil Company of California, the

voltage output of which is substantially proportional to the rate of change of pressure, and thesame may be used as part 6. The voltage pro-j duced by pickup 6 passes through channel iijto Another object is to provide a detonation meter ll filter 8.

I have been using a very satlsfac- While channel 5 has been shown diagrammatically as a single line. as are the other channels in Figures 1 and 2, it should be understood that actually two. wires, 8. wire and a ground, or other coupling means such as condensers maybe employed by those skilled in the art without inven-- tion, and that for an illustrative embodiment of the channels used reference should be made to the wiring diagrams of Figures 3 and 4.

Directly over channel 1 in Figure 1 appears a graph 9 of the voltage generated by the pickup, shown with a zero voltage axis extending in time from left to right on which the amplitude of the voltage from time to time is plotted graphically. High frequency vibration I is caused by the clatter of the intake valve closing, high frequency vibration I by the exhaust valve closing, and the low frequency wave I2 is caused by the explosion of the fuel and the resulting pressure rise and fall during the power stroke. Superimposed on low frequency wave |2 is high frequency wave l3 caused by the detonation, or knocking, which it is desired to measure. The amplitude of waves l3 denote the violence or intensity of the knock in direct proportion to their height. The great frequency however makes only such a faint blur on a cathode ray oscillograph tube that changes so very rapidly in amplitude and lasts such an instant of time that direct measurement is physi-' cally impossible.

The other voltage graphs are made on approximately the same scale as graph 9.

The filter 8 can be a high pass filter because with the usual values most of the energy of waves I0 and H lies below about 4000 cycles and that portion above 4000 cycles is much smaller in amplitude and energy than wave I3 which contains high energy bands at about 6500 cycles and between about 12,000 to 17,000 cycles per second, and the wave I2 is of much lower frequency. It is preferred however to use a band pass filter as filter 8 consisting of a tuned transformer coupling to increase the discrimination so that wave i3 will be of much greater amplitude than waves I8 and H as shown at M, which is a graph of the waves transmitted along channel l5 from the filter 8 to the amplifier and threshold "5.

The amplifier and threshold l6 cuts out waves l0 and H by means of a negative bias on the grid of the first tube of a pulser l1 and amplifies wave |3. Therefore the wave |8 transmitted over channel I9 from amplifier and threshold I8 to pulser consists entirely of wave l3.

Pulser II actuated by Wave l3 produces one single pulse for each cycle l2 that has a knock l3 of suificient intensity to overcome the threshold bias. Each pulse 20 decays exponentially and the pulser returns to its original state after the rest of the particular wave train that excited the pulser has passed but before the next wave train l3 arrives. While in mathematical theory a remainder is left in exponential decay, in fact pulse 20 is soon terminated completely. Pulses 20 have an amplitude E proportional to the maximum amplitude of wave I3.

Pulses 20 are carried from pulser H to accumulator 2| by channel 22, and the addition of each pulse causes the voltage 23 transmitted by the accumulator to a voltmeter 24 by channel 25 to increase by an amount 26 proportional to the amplitude of 20 and in turn of i3 and therefore directly proportional to the intensity of the detonation. A vacuum tube type voltmeter is preferred.

Pulses 28 are also carried by channel 21 to a rectangular pulse generator 28 which may be any of several well known types, but preferably is a multivibrator in which the first multivibrator tube is biased negatively beyond cutoff.

For each puke 220 received through channel 21 rectangular pulse generator 28 produces one rectangular pulse 29 which is transmitted along channel 38 to a counter and discharger 3|. Pulses 29 are of constant amplitude, constant duration, and therefore of equal area. They accumulate in a condenser in the counter and when a predetermined number 12 have accumulated the discharger is actuated to discharge the charges built up by n pulses 20 in accumulator 2|, the charges in 2| being drawn off by way of channel 32. The hand 33 of voltmeter 24 then returns to zero and is moved to indicate the sum of amplitudes E of the pulses by each pulse 20. The characteristics of the elements making up the counter and discharger can be selected so that n can be any integer, but for practical purposes n is selected as five or six.

Figure 2 shows a modified form of the invention. Parts 6 to I5, 24 and 33 having been described above will not be further described.

Channel l5 carries the same wave H as in Figure 1. The amplifier and threshold and pulser have been placed together in a single box 34 to save space, and produce a pulse 35 similar to pulse 20 for each power cycle of the engine containing a wave train |3 above the threshold value. The division of the circuit into functional elements in boxes like 34 is merely to aid in understanding the invention as sometimes the same element, such as a condenser, may be part of more than one functional element, and of course, the whole circuit operates as a. unit in some respects. Pulse 35 has amplitude e proportional to the intensity of the knock and the amplitude of wave l3.

Pulses 35 are transmitted over channel 38 to a square pulse generator of constant height 31 which generates a rectangular pulse 38 of constant height and duration. Pulses 35 are also transmitted over channel 39 to a biasing voltage generator 40, which preferably is an integrator producing pulse 4| of amplitude Ke proportional to the intensity of the knock. For each pulse 35 a single pulse 38 and a single pulse 4| is generated.

Pulses 38 are transmitted over channel 42 to square pulse generator 43 and pulses 4| are transmitted over channel 44 to put a bias on generator 43. Generator 43 generates a variable height rectangular pulse 45 for each pulse 38 it receives. Pulses 45 are of equal duration and their amplitude is proportional to the amplitude of wave l3, pulse 35 and pulse 4| and therefore directly proportional to the intensity of the knock, or detonation. The height Ke of pulses 45 is set by the biasing pulse 4| and generator 43 acts as a clip,- ping circuit to clip pulses 38 to proper height to form pulses 45. 1

Pulses 45 are transmitted by channel 48 to accumulator 41 where they accumulate in a condenser. The voltage of the condenser rises as shown at 23, 26 in Figure 1, and from 41 the voltage passes along channel 25 to voltmeter 24, 33 all as in Figure 1.

Pulses 38 are transmitted over channel 48 to accumulator and discharger 48 and when n of pulses 38 have accumulated in 49, accumulator 41 'is discharged through channel 50. Parts 31, 48, 49, 50 and 41 have the same function in Figure 2 as parts 28, 38, 3|, 32 and 2| have in Figure 1.

transformer coils 55 and 59. Parts 53, 54, 55-

and 56 act to form a band pass filter tuned to the frequency of detonation wave I3 and these parts are represented by part 8 in Figure 1.

The lower end of coil 56 is grounded at 51 and V the upper part of the coil leads to grid 58 of amplifying tube 59. There are two stages of amplification correspondingto grid 58 and grid 68. Tube 59 is shown as a duo-triode tube such as a 7F? which is employed to reduce the number of tubes employed. However, grids 58 and 68 may be in separate single triode tubes without departing from the invention and as the only function being accomplished at this point is that of amplification obviously many other amplification circuits will be suggested to those skilled in the art without involving invention. The circuit elements all being obvious in function such as coupling condenser M, the circuit of Figure 3 will not be described in minute detail. The threshold preventing the passage of waves below a. predetermined minimum amplitude is provided by potentiometer 82 which places a negative bias on grid 63 of pulser tube 68. Parts 58 to 83, inclusive and related parts therefor form an amplifler and threshold like It of Figure 1.

Tube 88 is shown as another duo-triode tube but grid 88 is tied to cathode 68 to make that portion of the tube form a diode with plate 67. Obviously, in place of all the double tubes shown in Figures 3 and 4, single tubes could be substituted which would merely increase the number of tubes. Parts 68 to 87, inclusive, form a pulser such as H of Fig-ure. 1. While not shown in Figure 1, I find it desirable to have amplifying tubes 88 and 89 and a rectifying tube I8 in the circuit leading to condenser TI. Condenser ii is the heart of the accumulator 2i of Figure 1 and rectifier I8 is part of the accumulator because it acts to keep the charges on condenser II.

As the time between pulses 28 is sometimes several seconds some leakage from condenser II would occur which would result in a reduced false voltage being indicated at 33. To prevent this a compensating and regulating circuit embodying tube I2 and resistances I8 and 74 is connected to condenser I! and may be regarded as part of accumulator 2|. Current from plate '15 of tube Iii flows to the cathode and through resistance I9 to ground, the amount of current being governed by the charge in condenser II applied to grid I8. This current in I8 creates ayoltage at the top of I9 that is slightly greater than the voltage in II at all times as when the voltage of III increases so does this current, and therefore a very small current flows in condenser II through resistance I4 to replace the charge lost by leakage so that the voltage in ll is substantially constant between pulses 28 and is only raised as at 28 by the next pulse 28 coming in through tube "I0. A lead TI transmits the voltage at the top of I9, which is substantially that of condenser III to a voltmeter 24 preferably of the vacuum tube voltmeter type which is not shown in Figure 3 but is shown in Figure 4.

Pulses 28 are transmitted over channel 27, of which wire I8 of Figure 3 is a part to a rectangular pulse generator 28 to be described now. Tube I9 is a conventional triode employed to amplify the pulses, but its chief function is to couple the pulse generator 28 to the pulser Il without any feedback. Generator 28 consists of a multivibrator formed of two triodes 88 and 8| with the grid of each triode connected to the plate of the other triode through condensers 82 and 83. A negative bias is placed on the grid of triode 88 by resistance 84 biasingthe grid beyond cutoff. A positive pulse such as 28 on the grid of triode 88 overcomes this negative bias and regardless of the size of the pulse 28 a uniform pulse 29 is transmitted through condenser 85 through diode rectifier tube 88 to accumulate on condenser 81. The tube 86 is shown as a triode but wiring the grid to the cathode has made it a diode.

The counter and discharger 8| of Figure 1 may consist of tubes 88, 88, 89 and 98 and related parts such as condensers 81 and 9|. The pulses 29 add to the charge on condenser 81 and triode tube 88 compensates for any leakage from the condenser 81 the same as tube I2 compensates for leakage from the condenser II,

parts 92, 93 and 94 corresponding to parts I3, I4 and I5 respectively in this mode of compensation. Resistance 92 has an added function over resistance I3, which will now be set forth.

A movable tap 95 is provided to take any portion, or all of the voltage developed across resistance 92, which voltage is substantially the same as that on condenser 81. Tap 95 leads to the control grid of gas filled thyratron tube 98. By moving the tap the number of pulses 29 on condenser 81 necessary to fire the thyratron tube 98, that is to make tube 98 conductive of current from plate 98 to cathode 91, may be varied. The number of pulses on condenser 87 to fire tube 98 is referred to as n, and is usually set at 5 or 6, but may be any positive integer from 1 to any desired upper number, very high numbers requiring more exact values of the circuit characteristics'than lower numbers.

Plate 98 leads to discharging wire 98 and when tube 98 fires, or discharges, the charge on condenser II drains off through 98, 98, 91 to ground 99, a portion of the charge surging into condenser 9| which makes grid I88 go positive enough to fire gas filled thyratron tube 89. When tube 89 becomes conducting the charge on condenser 81 discharges through plate I8I to cathode I82 and then to the ground at I83.

In Figure 3 the heating filaments for the cathodes are not shown to reduce the complexity of the drawings, but of course each cathode-has them. Wires ending in 32+, 33* receive suitable positive voltages and the wire marked Crreceives a suitale negative voltage relative to the ground from a power supply, such as shown in Figure 5.

Condenser I88 in Figure 3 extinguishes tube 98, that is, makes the tube non-conducting from plate to cathode when the charge from condenser 'II has gone to ground thus preparing condenser 'Ii to receive and hold the next pulse 28. Condenser I85 performs the same function for tube 89 and condenser 81.

Figure 4 shows the modified form of the detonation meter shown in diagrammatic form in Figure 2. While Figs. 1 and 3 are the preferred form, Figures 2 and 4. have obvious advantages making them a valuable modification.

amass? In=l igure 4 wires I03 and I01 are leads comin from the pick-up and powdered iron core I88, coils I33, III and condensers III and H2 form the filter 3 of Figure 2 being a tuned transformer band pass filter and coupling. Triodes 3 and H4 furnish two stages of amplification and potentiometer II3 provides a threshold bias setting a lower limit in amplitude as to waves that will pass to coupling condenser H6 and the rest of the circuit. Tube III containing a triode and a diode forms the pulser included in 34 of Figure 2 with the amplifier and threshold.

The square pulse generator of constant height 31 consists of triodes H8 and H3 and related circuit elements which form a multivibrator generatin pulses 38.

Pulses 33 from pulser III also are transmitted I28, a rectifying and integrating triode I26 and an accumulating condenser I2I.

The voltage of the charge on condenser I2I is measured by voltmeter 24 shown as a vacuum tube voltmeter having duo-triode tube I28, leads I29 and I30 to the indicating instrument 33 and related circuit. elements.

Wire I3I transmits pulses 38 of constant amplitude from tube II8 of the generator 31 to the accumulator and discharger 43. Accumulator 43 comprises a buiIer triode I32, a rectifier and integrating triode I33 and an accumulating con denser I34. Pulses 38 accumulate on condenser I34. The similarity of parts I25, I26, I21 and I32, I33 and I34, respectively, is obvious.

The voltage on condenser I34 is transmitted to the grid of gas filled thyratron I36 and when the proper value is reached fires tube I36 and discharges condenser I2I through plate lead I31 and cathode lead I38 to ground. This discharge sends' a pulse through condenser I33 to the grid of a second gas filled thyratron tube I40 and fires tube I40 which discharges condenser I34 to ground through plate lead I and cathode lead I42. Condensers I43 and I44 act as condensers I04 and I05 of Figure 3 to bring their respective thyratron tubes I36 and I40 back to non-conducting state after their discharge.

No compensating tubes like tubes I2 and 88 of Figure 3 are shown because these compensating tubes and circuits are not essential in either Figure 3 or 4. They may be added to Figure 4 by one skilled in the art after studying Figure 3 if their use is deemed desirable, and when the time between knocks is very long their use is desirable.

In Figure 5 a source of power generally designated I45 is shown. However any power source, such as radio A, B and C batteries could be used instead, and Figure 5 is merely presented to make the disclosure very complete.

Power source I45 is the type now used. A 110 volt 60 cycle power line I46, or any other suitable alternating current source is provided with the usual switches, fuses and other elements, and transformer coil I41. The rest of the transformer consists of iron core I43 and center tapped coils I43 and I30. The usual duo-diode rectifier tube I3I is connected as shown to coils I43 and I33 and may be the type tube. Condensers I32 and I33 bypass the sine wave ripple and resistances I34, I33, I33 and I51 have difierent voltages developed across them and act as voltage dividers. Wire ends marked 31+, 32+, 83+, C1- and C:- supply diflerent' voltages positive or negative to ground as indicated by the or signs, and these voltages are applied respectively to like designated wire ends in Figures 3 and 4. Tube I38 is a voltage regulator tube of any ype and may be a gas filled tube known as VR. 150.

The power source for the cathode heater filaments of Figures 3 and 4 (not shown) is also not shown as any of the usual radio tube filament heater power sources may be employed to develop the voltages designated by the vacuum tube manufacturer.

Operation In Figures 1 and 3 pick-up 3, 3i and 32 generates voltages substantially directly proportional to the rate of change of pressure in the cylinder, and plotted on a time axis these voltages form a wave 3 having valve clatter I0 and II, power stroke pressure changes I2, and if conditions are rig-ht, every second or two the wave will contain detonation wave I3, which is caused by a knock. The method of measuring wave I3 only, and the apparatus for doing so are part of my invention.

Wave 3 is passed through filter 8, 83, 54, 53 and 56 which substantially completely eliminates wave I2, passes wave I3 and at least partially suppresses waves I0 and II so that wave I3 is the only wave left of any considerable amplitude. This is shown as wave I4.

Wave I4 is passed through an amplifier and threshold I6, 59, 60 and '32 which amplifies wave I3 and cuts out waves I0, II and I2 completely. The isolated wave I3 is shown at I8 in Figure 1.

Wave I8 is passed into pulser I1, 33 and 33 which generates a pulse 20 of amplitude E directly proportional to the highest amplitude of wave I 3. This pulse 20 is amplified at 38 and 33 and passes through rectifier I0 to accumulate in accumulator condenser 2 I, I I

Pulse 20 also passes into rectangular pulse generator 28, 80, 8I, 82, 83 and 84 which generates for each pulse 20 of any amplitude a constant height and duration pulse 23.

Pulse 23 passes through rectifier 83 to accumulate in condenser 81 of counter and discharger 3|. Depending on the setting of potentiometer 32, 35 a. number n of pulses 23 raise the voltage of 81, 93, 35 to the point where thyratron 30 suddenly becomes conducting. 'I'hyratron 33 discharges condenser II and fires thyratron 83 which discharges condenser 81. Surges in condensers I04 and I05 make the thyratrons 80 and 88 respectively non-conducting and return the system to its original condition.

Vacuum tube voltmeter 24, 33 and 11 indicates the voltage of condenser I I, and as the capacity is known, and as the voltage rise is proportional to the intensity of the knock, the dial 24 may be calibrated in knock intensity values. However, any other desired calibration or division of the dial may be made. In practice when testing the octane numberof a asoline the amounts or fuel and air are varied (not shown) until knocking results. The knocks do not occur every power stroke, but instead may be one every twenty or so power strokes more or less and may be a second or two or even more apart. The hand 33 jumps to a. new position with each knock above the threshold value and holds its position long enough for rapid reading. When the nth knock arrives the hand 33 jumps back to zero.'

The operation of Figures 2 and 4 is similar to the operation of Figures 1 and 3 but differs In the handling of pulse 35 of Figure 2 which is similar to pulse 20 of Figure 1.

Pulse 35 passes into a square pulse generator 31, H8, H9 which generates a constant height and duration pulse 33 for each pulse 35 received regardless of size of pulse 35.

The constant pulse 38 is clipped to amplitude proportional to 35 and I3 in square pulse generator 43, I22, I23, forming pulses 45.

Pulses 45 are accumulated in condenser I21 of accumulator 41, I25, I26 and I21, and the voltage of I2! is indicated by vacuum tube voltmeter 24; 33, I28, I29 and I30 the same as in Figures 1 and 3.

In Figures 2 and 4 pulses 35 actuate biasing voltage generator 40, IN to modulate tubes I22 and I23 to regulate the height of pulses 45 so that they are proportional to the intensity of knock wave I3.

Uniform pulses 38 are accumulated on condenser I34 of accumulator and discharger 49, I32, I33, I33 and I36, and when n have accumulated thyratron I36 is fired discharging condenser I21 and firing thyratron I40 which discharges condenser Il34. Condensers I43 and IN restore the system to its original condition. The action of the parts described in this paragraph is similar to the action of parts 89, 90, IIM and I of Figure 3.

The operation of Figure 5 is so well understood as to need no further description, it being described above.

As pointed out above many changes of circuits following the usual circuits old in the art, and many substitutions of difierent tubes, conventional elements or units having the same function, may be done by those skilled in the art without departing from my invention, the scope of which is set forth in the following claims.

Having described my invention, I claim:

1. A method of indicating the knock level in a cylinder of an internal combustion engine comprising the steps of generating a first series of electrical pulses the amplitudes of which are proportional to the rate of change of pressure in the cylinder, eliminating from said pulses all frequencies substantially lower than the frequencies of detonation and eliminating all of said pulses below a predetermined minimum amplitude to form a second series of electrical wave train pulses, generating for each pulse of said second series a third series single pulse proportional to the amplitude of said pulse of said second series, generating for each pulse of said second series a fourth series single pulse of uniform value, accumulating said third series pulses and indicating the sum of said accumulated third series pulses, accumulating 11. pulses of said fourth series pulses where n is any predetermined integer and upon the accumulation of npulses of said fourth series pulses discharging the accumulation of said third and fourth series pulses whereby this method may be repeated.

2. A method of indicating the knock level in a. cylinder of an internal combustion engine comprising the steps of generating a first series of pulses synchronous with, proportional in amplitude to the maximum rate of change of pressure in the cylinder, and of substantially the same frequency as the detonation pressure waves in said cylinder, eliminating all of said pulses below a predetermined minimum amplitude to form a second series of pulses, generating for each pulse of said second series a third series single pulse proportional to the amplitude of said pulse of said second series, generating for each pulse of said second series a fourth series single pulse of uniform value, accumulating said third series pulses and indicating the sum of said accumulated third series pulses, accumulating n pulses of said fourth series pulses where n is any predetermined integer and upon the accumulation of n pulses of said fourth. series pulses discharging the accumulation of said third and fourth series pulses whereby this method may be repeated.

3. A method of indicating the knock level in a cylinder of an internal combustion engine comprisin the steps of generating a first series of pulses synchronous with, proportional in amplitude to the maximum rate of change of pressure in the cylinder, and of substantially the same frequency as the detonation pressure waves in said cylinder, eliminating all of said pulses below a predetermined minimum amplitude to form a second series of pulses, generating for each pulse of said second series a third series single pulse proportional to the amplitude of said pulse of said second series, accumulating said third series pulses, indicating the sum of said third series pulses, counting said third series pulses and when 11. third series pulses ar accumulated where n is any predetermined integer discharging the accumulated third series pulses.

4. The method of measurin the knock intensity during periods of detonation in the cycles of an internal combustion engine cylinder, comprising the steps of continuously picking up a signal during all cycles in synchronism therewith, the signal containing first elements which are a function of knock intensity during periods of detonation, the signal also containing other elements, clearing the signal of substantially all elements except the first elements, clearing the signal of all the first elements below a predetermined fixed value, accumulatin n cycles of said remaining first elements where n is any predetermined fixed finite integer and indicating a function of said 11. cycles of said first elements.

5. A detonation meter for indicating the intensity of knocking synchronous with the power stroke cycle in the cycles of an internal combustion engine cylinder, comprising in combination pick-up means for continuously picking up signals proportional to the intensity of knocking during the power stroke cycle, and spurious signals during other cycles, means for cutting out the signals picked up durin said other cycles, means for cutting out signals during the power cycle below a predetermined value, means for accumulating a series of 'n of the remaining power stroke cycle signals where n is any predetermined integer, means for discharging said accumulation when n of said power stroke cycle signals have been accumulated.

6. The method of measuring the knock intensity of a cylinder of an internal combustion engine comprising picking up signals for each combustion cycle containing elements proportional to the knock intensity in said cylinder, generating a rectangular pulse for each combustion cycle said rectangular pulses being of constant amplitude, integrating said signals to form aseass'r biasing pulses of amplitude proportional to the knock intensity, clipping said rectangular pulses to the same amplitude as their respective biasing pulses, accumulating n of said clipped rectangular pulses where n is a predetermined integer, and indicating the value of said clipped rectangular pulses.

7. The method of measuring the knock intensity of a cylinder of an internal combustion engine comprising picking up signals for each combustion cycle containing elements proportional to the knock intensity in said cylinder, generating a rectangular pulse for each combustion cycle said rectangular pulses being of constant amplitude, integrating said signals to form biasing pulses of amplitude proportional to the knock intensity, clipping said rectangular pulses to the same amplitude as their respective biasing pulses, and indicating the value of said clipped rectangular pulses.

8. A detonation indicator for a cylinder of an internal combustion engine comprising in combination a pick-up for generating voltages substantially directly proportional to the rate of pressure change in said cylinder, a filter connected to said pick-up for cutting out frequencies in said generated voltage of less than 12,000 cycles per second, amplifier and threshold means connected to said filter for amplifying said generated voltages of more than 12,000 cycles per second which have more than a predetermined amplitude, a pulser connected to said amplifier for forming single pulses corresponding in time with and proportional in amplitude to said generated voltages of more than predetermined amplitude, an accumulator connected to said pulser for accumulating said pulses, a uniform pulse generator connected to said pulser for generating a uniform pulse for each 01' said single pulses, a counter connected to said uniform pulse generator for counting 12 pulses where n is a predetermined integer and then discharging said accumulator and means indicating the sum of the amplitudes of the single pulses in said accumulator.

9. A detonation indicator for a cylinder of an internal combustion engine comprising in combination a pick-up, a filter connected to said pick-up, amplifier and threshold means connected to said filter, a pulser connected to said amplifier, an accumulator connected to said pulser, a uniform pulse generator connected to said pulser, a counter connected to said uniform pulse generator for discharging said accumulator upon the occurrence of n pulses and an indicator for indicating the electrical state of said accumulator whereby the knock level of said cylinder is measured.

10. A detonation indicator for a cylinder of an internal combustion engine comprising in combination a pick-up for generating voltages substantially directly proportional to the rate of pressure change in said cylinder, a filter connected to said pick-up for cutting out frequencies in said generated voltage of less than 12.000 cycles per second,- amplifier and threshold means connected to said filter for amplifying said generated voltages of more than 12,000 cycles per second which have more than a predetermined amplitude, a rectangular pulse generator connected to said amplifier for generating rectangular pulses of constant amplitude and duration spaced in time with said generated voltages, an integrator connected to said amplifier for integrating said generated voltages into single pulses proportional in amplitude to said amplified voltages, a clipper connected to said rectangular pulse generator for receiving said rectangular pulses, said clipper being connected to said integrator for receiving said single pulses as bias and clippin said rectangular pulses to an amplitude proportional to said amplified voltages according to said bias, an accumulator connected to said clipper for receiving said clipped rectangular pulses, a counter connected to said rectangular pulse generator for counting 12 pulses where n is a predetermined integer, said counter being connected to said accumulator to discharge the accumulator upon receiving n pulses, and means for indicating the electrical state of said accumulator whereby the average level of detonation in said cylinder may be determined.

, 11. A detonation indicator for a cylinder of an internal combustion engine comprising in combination a pick-up, a filter connected to said pickup, amplifier and threshold means connected to said filter, a rectangular pulse generator connected to said amplifier, an integrator connected to said amplifier, a clipper connected to said rectangular pulse generator, said clipper being connected to said integrator, an accumulator connected to said clipper, a counter connected to said rectangular pulse generator, said counter being connected to said accumulator, and means for indicating the electrical state of said accumulator whereby the average level of detonation in said cylinder may be determined.

12. In a detonation level indicator for internal combustion engines, a means for determining the sum of 1!. electrical pulses of variable amplitude coming from a pulser when n is any predetermined integer, comprising in combination a parallel channel network connecting said pulser and a pulse accumulator, a uniform pulse generator, a counter and a discharger in one branch of said parallel channel, said counter operating said discharger to discharge said accumulator when n uniform pulses are generated, and means indicating the sum of said variable pulses in said pulse accumulator.

13. In a detonation indicator in which variable pulses are generated by detonation in an internal combustion engine, means to indicate a parameter of said detonation comprising means to accumulate and integrate said variable pulses, a second pulse generator generating a uniform pulse for each variable pulse, means to count the uniform pulses, means to discharge both the uni- .form and the variable pulse accumulator when the pulses number n, where n is any predetermined finite integer, and means to indicate the sum of the variable pulses.

14. In a sub-combination as disclosed, means for converting vibrational and pressure waves containing desired and undesired components into electrical signal currents, a high pass filter circuit fed by said means, a vacuum tube amplifier having an input and an output circuit connected to said filter circuit at its input circuit, and means in said input circuit providing an adjustable fixed operating threshold whereby signal currents of a magnitude below selectable fixed desired values do not pass to the output circuit of the amplifier.

15. The method of indicating the detonation intensity level of a cylinder of an internal combustion engine comprising generating an electrical pulse proportional to the maximum rate of change of pressure in the cylinder due to each detonation, discarding all of said pulses of less than predetermined amplitude, adding the amplitudes of n of said pulses of sufficient amplitude where n is any predetermined finite integer DESLONDE R. DE BOISBLANC.

14 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PAT NTS Number Name Date Frankfurter Aug. 1, 1922 Hopkins July 17, 1923 Germond Aug. 6, 1935 Fitz Gerald Mar. 1, 1938 White Apr. 5, 1938 Engbert et a1. July 15, 1941 Eldredge Dec. 21, 1943 Traver et a1. Feb. 1, 1944 Crossley et a1 Feb. 25, 1947 

